Shaft mounting



June s, 1926.

A. MCNAB SHAFT MOUNTING Filed Dec. 8. 1925 2 Sheets-Sheet 1 ATTORNEYMmm/a BVM @M June 8,1926. l 1,588,251

A. MCNAB SHAFT MOUNTING cq cn Filed Dec. 8. 1925 2 Sheets-Sheet 2Patented June 8, 1926.

UNITED srares ALEXANDER MCNAB, y01E" BRIDGEPORT, CONNECTICUT.

SHAFT MOUNTING.

Application med December s, 192,5. serial- No. 74,073.

This invention relates to shaft mountings such as the tail shaftmountings of power driven vessels and is particularly intended toprovide an improved form of the construction' of the device described inmy U. S.`

Patent No. 1,315,677.

The device described in that patent relates to a systemV of pressurelubrication for a tail shaft, the mounting being designed to prevent theentry of salt water or deleterious material into any part of saidmounting.

The damage caused by the entry of salt water carrying sand or grit intothe tail shaft mounting needs no emphasizing, but it may not begenerally understood that the water in some localities is corrosiveowing to the decomposition of vegetable or other organic matter. i

Briefly describe-d, the tail shaft mounting described in my patentreferred to andv utilized incarrying out the Vpresent invention is soconstructed that the space between the usual stern tube and the tailshaft mounted therein, is being supplied with a lubricating medium, andsuitable glands are arranged at the inboard and outboard ends oi thetube designed to prevent the egress of lubricating fluid. It has beenfound in practice, however, that owing to the rapid fluctuations of thepressure effective on the outboard end of the stern tube, due to thepitching of the vessel, that it is practically impossible to preventloss of oil through the outboard end of the mounting, since a. pres,-sure suiiicient to keep out'water when the stern tube and tail shaft aresubmerged at a maximum dept-h below the'water line, is so high that thelubricant is liable to be forced through the after gland when theeffective pressure is materially reduced or entirely removed, due to thepitching of the vessel, when of course the propeller may be lifted clearof the water. It has further been found by experience ythat although therear gland may form a satisfactory closure against the entry of waterunder normal conditions, yet under extreme conditions of rapidfluctuations of pressure, a certain amount of water will enter despitethe rings or other packing devices employed. .The

entry of water, frequently carrying abrasive material such as sand, ofcourse to a certain extent nullifies the advantages otherwise gained bythe provision of anoil lubrication system, since labor is involved indismounting` the packing rings at the tail end of the shaft in order todraw the shaft for renewal of liners or bushings `and the removal ofpitting, score marks, or grooves worn by .such abrasive material, whilethe water itself may cause serious corrosion.

The object of theinvention is to provide an oil lubrication system fora. tail shaft mounting in which the pressure of the oil V.supplied tothe mounting shall be automatically varied to-equalize fluctuations ofpressure at the outboard end of the tail shaft, thus preventing loss oflubricant and entry of water and deleterious material.-l

A further object 'of the invention is to provide an o-il lubricationsystemv for a tail shaft mounting in which the pressure of the oilsupplied to the mounting is automatically controlled yby the pressureexerted by the waterr on the outboard end of the mounting at whateverdepth below the waterline the outboard endrof the propeller may happenyto be. o Y

"A still further object of the inventionis to provide .an oillubrication system for a tail shaft mounting in which the pressure ofthe oil supplied to the mounting is automatically varied, according tothe pressure of the water effective on the outboard end of the tailshaft, by a mechanism of maximum simplicity'and of a minimum number ofworking parts. p

In the accompanying drawings a preferred form of the invention isillustrated by way of example but it will be realized that variousconstructional modifications of the apparatus shown may bereadilyeiiectod by those conversant withl the art and is not desred,therefore, to limit the scope of the invention in any way to vtheembodiments illustrated and described but only yas 'defined by theappended claims.

Figure l is aside elevation partly in 'sec-v tion of a tail shaftmounting fitted withthe device of my invention. y i

(lll

Figure 2 is a perspective view in section on the line 2-2 of Fig. 1 ofthe oil retaining packing.

Figure 3 is an enlarged view in cross section on the line 3--3 of Fig. 1of the control cylinder. I

Fig. #l is an enlarged view partly in section of ai shaft mounting inwhich an alternative form uf packing is utilized.

ln thel drawings 'ly denotes the. taill shaft and 2 the stern tube.Arecess 3 adapted to contain lubricant between the surfacewof the tailshaft and the stern tube, is provided by the normal clearanceprovided'for the insertion of liners between the shaft and tube or bythe clearance between'the'inner surface of the Vtail tube and `shaft asprovided in standard practice. AA bushing, 4 is placed between,thereoess3 and the inboard packing gland 5 while'a liner 14 is-ca'rried in abushing 12 at the outboard side of said1 recess. Bushings d and 12 areheld' against 1ongitudinal movement in any suitable manner, in theconstruction illustrated, bushing d being held against a shoulder on thestern tube by the packing of vinboard gland 5 while the outboard bushingis held in place by the abutment of a flange thereon against the end ofthe vstern tube.

To prevent loss of oil under normal cir-r cumstancesfrom the outboardend of the tail shaft bearing, the oil retaining. construction tion(Fig. 2), comprises an oil' retaining ring or rings "6 together withflexible rings 7 clamped to the end of the sterntube and bearingagainstthe surface of the tail shaft. In the construction illustrated vin Fig.1 a plurality of rings 6. is provided and' is mounted on the tail shaftso as to rotate therewith either by beinga driven fit thereon or bybeing keyedthereto, which latter method 'is preferable since it providespositively that the rings will rotate with the tail shaft. .The rings,which may be of'any suitable forin used for pressure retaining purposes,are. shown of U-shape` in cross section, this form having proved verysatisfactory in actual use. The rings engage in grooves formed incollarsSl, a separate collar preferably being provided to (3o-operatewith each ring, and for ease of assembly' being formed in two parts 81,82. A water tight joint to prevent entry of` water radially through therings is provided lfor by arrangement of washers 9l of-iber, rubber, oilimpregnated paper, or other suitable mate-- rial, between the rings. Theentry of water along the shaft between. the rings and the surface of theshaft `is prevented by flexible washers 10, two such washers are shownin l? ig. 2, the inner washerA 11 being of 'felt while .the outer4washer` 10 vmay 'be of "rubber impregnated material or other'. suitablecoin,-

position, these washers 10, 11 may be held in place by an end ring 13.All of the rings` and washers are conveniently mounted upon the end ofthe stern tube by means of bolts 111 threaded into the end of the sterntube and having their outer ends tapped to take nuts 15 which may bescrewed up against the end ring and thus clamp the whole assemblysecurely in place.

The. usual-rope, guard 16 is shown mounted upon the stern nut '17.

alternative form of this oil retaining packing which has been found tohave considerable advantages in certain respects is illustrated in Fig.l in which 18 represents a ring containing member pro-vided with grooves19 in which are mounted the oil retainingrings 20,21. `Part 18 is boltedto the propeller boss 22 and projects into a casing 29 bolted to vt-heend of the stern tube. construction is of course a considerablesimpliiic'ation of that just described .but has been found to answersatisfactorily vfor many draft. In this form a white metal liner 24C isprovided at the inboard and outboard end of the stern tube,` a heavyring of white,V metal25 being provided adjacent the extremities thereofand held in a groove formed in the stern tube. A ring containing member23 may be employed, as illustrated in Fig. d, at the inboard end of thestern tube. ln this case the part 18 is bolted to the of the generaltype described in my` prior* nut 26 on the inner end of the stern whilethe .patent 1,315,677 is utilized. This construcpart 1.8 is keyed orotherwise'secured to ro tate with the tail shaft. f

The problem to be solved is to supply lubricant to the recess 3 in suchway that loss of lubricantfoutwa-rdly through the packing rings or entrykof water inwardly through said rings is prevented. This problem in-`volves the supply of lubricant to the recess 3 under a pressure whichwill practically perfectly compensate or be equal to the pressure of thewater acting upon the outboard end of the tail shaft mounting. Thepacking at the inboardend of the tail shaft is subjected to much lessvibration than the outboard end and can be maintained suitieienty tightto prevent loss of lubricant under any pressure met in practice.

To satisfy these conditions,` according to the invention, lubricant issupplied to the tail shaft mounting under a pressure controlled by thepressure ofthe water acting on the outboard end 'of the stern tube. l

The means by which this result is achieved in the construction shown inFig. 1 comprises a lubricant reservoirv27 from which oil is pumpedby anysuitable power driven pump 28 through the conduit 29 t the recess A3.Advantageously the pump may be driven directly from the. shaft 1 asshown. A conduit 3D leads from the recess to the compensating cylinder3l. Thisy cylinder contains a floatingpiston 32 serving to diloo videthe interior of the cylinder into two portions, the upper of whichcontains water under the same pressure as that. acting' on the outboardend of the stern tube. for this purpose the upper end of the cylinder isconnected by the pipe 33 to an outlet at approximately the level of thesaid end of the stern tube. Pipe 30 opens into the lower portion of thecylinder and this portion of the cylinder is` also connected to thelubricant reservoir by pipev-B. The function of piston 32 is to controlthe flow of lubricant back to the lubricant reservoir 27 according tothe pressure of the water in the upper port-ion of the piston. Thisresult may be effected in several ways, as illustrated in Fig. 3, pipes29, 30, and 35 are of a size sufcient to carry the greatest ow oflubricant that has to be provided for. The pipe 35 opens into the lowerportion of cylinder by means of elongated orifice 3a which may belsubstantially closed or completely opened Aby the movement of thepiston, which is of sufficient depth to at all times seal this orificeagainst entry of water. This construction provides a very desirablesimplicity and surety of operation since it comprises only one movingpart positively operated in both directions by the pressures serving tocontrol the functioning of the device. It will be readily understoodthatr the nearer the outboard end of the stern tube is lifted to thewater line the less will be the pressure acting down wardly on thepiston 32 which will accordingly be forced upwardly through the pressureof the oil acting on its under side until the orifice leading to pipe 35is open to an extent such that the oil flows through the pipe'in such away that the pressure in recess 3 falls until equal to that in the upperportion of the cylinder and therefore to that of the water acting on theouter end of the tail shaft mounting; while when the outboard end of thestern tube is lowered into the water so the pressure acting upon theupper side of the piston 32 is increased, the opening of the orificeleading to pipe 35 is decreased and the pressure in the recess 3automatically increased until equal to the ln'essure of the water actingon the outer end of the tail shaft mounting. It is to be understood ofcourse that the pump serving to circulate the lubricant is of a capacitysunicient to pump a volume of lubricant under a pressure which willbuild up rapidly a pressure in the tail shaft mounting equal to themaximum pressure of the water to be exc pected in practice.

Various refinements which lmay be found desirable may of course beincorporated as will be understood by those familiar with the art, suchfor instance as a by-pass valve to avoid excess pressure inthe pipeline, or valves in the various pipes to enable the capacities thereof tobe varied as for instance may be found desirable in adapting one size ofapparatus to a range of tail shaft mountings of various constructionsfor vessels of differing different draft or to meet other variations metwith in practice.

ln some circumstances it might be found expedient to. replace theconduit connecting the control cylinder to the outside water by someother device such as an electric switch operated by the variations ofpressure to open or close the outlet port in the control cylinder'.Further, it mightbe found advantageous to provide spiral grooves to leadlubricant to the various surfaces in frictional contact and in Fig. lsuch groot/es are shown arranged in theafter bushing and in the sides ofthe oil retaining rings at 36.

As :before stated it will be obviousthat various constructionalmodifications of the described apparatus may be readily made and it is,therefore, to be understood that the invention is not to be in any wayrestricted to the constructional forms described or illustrated, butonly as defined by the scope of the appended claims.

lWhat I claim is l. tail shaft mounting comprising in combination a tailshaft, a stern tube, a lubricant containing chamber arranged betweensaid tail shaft and sterntube, means to supply lubricant under pressureto said lubricant containing chamber and means to control the pressureof the lubricant in said chamber, said pressure control means respondingto variations in the pressure of the water acting upon the outboard endof said tail shaft mounting.

2. ,A tail shaft mounting comprising in combination a tail shaft, astern tube, a lubricant containing chamber arranged between said tailshaft and stern tube, means to'supply lubricant under pressure to saidchamber, and means to control thev pressure of the lubricant in saidchamber, said control means being actuated by the water pressure actingupon the outboard end'of said tail shaft mounting.

3. A tail shaft mounting comprising a stern tube, a lubricant containingchamber arranged between said tail shaft and stern tube, a power drivenpump to supply lubricant under pressure to said chamber, ay conduitconnecting said power driven pump to a lubricant reservoir, av conduitconnecting said power driven pump to said lubricant containing cham-ber,a conduit connecting said lubricant containing chamber Vto a cylinderdivided into two portions by a floating piston, an outlet port for saidportion of the cylinder and means whereby said piston is moved accordingto variations of presi' in sure due to varying'depth of the outboard endof the tail shaft mounting below the water level to vary the opening ofsaid port. 4f. A tail shaft mounting as claimed in claim 2 in which thefloating piston 1S moved to vary the opening of the outlet port for thelubricant Containing portion of the control cylinder by the pressure of.Water contaned in another portion of said cylindei" exerting on saidpiston substantially the same pressure as the Water at the otboard endof the' tail shaft mounting,y the Water containing' portion ofsaidoyl-d'e'r beg'h communication by :loopen oohd W'th'the 16 outside of thevesseli at substantially the same level as the outboard end of the tailshaft mou'nfng.

Signature. l Y

ALEXANDER MCNABQ

